Keeping the lid on while boiling is a bad idea. Even with extract there is a risk of DMS (cooked corn and vegetable flavors and aromas), boiling drives this off, but with a lid on it'll go back in your beer. In addition, if you keep the lid on you're much more likely to get boilovers.

The main reason I stated earlier about the commercial breweries is that they cannot remove the lid and the condensation drips back into their kettle. I understand they may have a fan pulling on the kettle but they don't have a way to remove the lid as we do, and their beers aren't butter bombs.

Installing a flexible metal duct and power vent doesn't seem like it would be difficult to make and give it a try. A metal flexible dryer vent pipe should work and be quite handy so you could swing it away anytime you wanted.

Added: I think I'd put a trap close to the lid, maybe a couple feet away and drill a small hole in it so any condensed steam could drain away from the brew pot. jmo....